The invention is directed to a grinding roller for pressure comminution of granular material, particularly for roller-type presses for inter-particle crushing, comprising a roller jacket with wear-resistant surface armoring that comprises alternating zones of highly wear-resistant material and interspace zones having a different wear resistance. The invention is also directed to a method for the manufacture of the grinding roller.
In roller mills, granular, brittle grinding stock is drawn into the nip by which the two rotatably seated, oppositely rotating rollers are separated from one another and are subjected to a pressure comminution therein. What is referred to as inter-particle crushing in the nip of a high-pressure roller mill or, respectively, roller press is also known, whereby the individual particles of the grinding stock drawn into the nip by friction crush one another in a product bed, i.e., in a material fill compressed between the two roller surfaces given application of a high pressure. It is self-evident that the roller surfaces are thereby subject to a high load and to high wear.
At least the following demands are made of such roller surfaces: They should have a high capability of resisting wear, should be capable of being cost-beneficially manufactured, should be able to be repaired by the operator or, respectively, customer and should also have a good draw-in behavior for the material to be comminuted.
It is known to make the roller surfaces of inter-particle comminution roller mills or, respectively, roller presses more resistant to wear in that a plurality of pre-fabricated, hard metal bodies such as, for example, burl bolts that can be embedded in corresponding channels or, respectively, blind bores of the roller jacket are arranged on the roller surface (EP-B-0516952, FIG. 2). Given what is referred to as this grid armoring, the burl bolts project outward from the roller surface with such a great height and are arranged with such a spacing from one another that the interspaces between the burl bolts remain filled with the compressed, fine-grained product material during operation of the roller mill, this forming an autogenous wear protection for the roller surfaces and exhibiting a good draw-in behavior due to the roughness thereof.
Whereas the welding of pre-fabricated burl bolts would only be possible for manufacturing the grid armoring given a weldable bolt material such as, for example, structural steel or the like, the fastening of pre-fabricated burl bolts in corresponding blind bores of the roller material is comparatively involved in terms of fabrication technology due to the material-removing processing and can practically not be repaired by an operator in case of damage.
EP-B-0659108 also discloses a surface armoring of press rollers having zones of highly wear-resistant material and interspace zones having a material with a different, for example lower wear resistance, whereby the highly wear-resistant zones are formed of lamina-like hard members manufactured by hot isostatic pressing that, like the interspace material composed of sinterable composite material, are secured to the roller member by a hot isostatic pressing process. Due to faster wear of the less wear-resistant interspace material, a profiling of the roller surface is supposed to occur during roller operation that has troughs or, respectively, interspaces arranged between the hard members that are filled with compressed, fine-grained material during operation of the roller press that, as autogenous wear protection, remains in the troughs or, respectively, interspaces between the hard members during the roller revolutions. It is self-evident that this surface armoring of press rollers cannot be repaired at all by an operator.
Further, EP-B-0563564 discloses a grinding roller for an inter-particle roller mill wherein the roller jacket is composed of a wear-resistant chill casting. Profiling weld beads are thereby welded onto the outside surface of the chill casting roller jacket, these beads potentially crossing one another, so that a lozenge-shaped weld bead grid pattern then arises for the purpose of achieving an autogenous wear protection. Apart therefrom that it is problematical to weld chill casting faultlessly, especially when the chill casting material contains a high proportion of carbon, chromium, etc., the fabrication of this chill casting roller jacket with subsequent, specific application welding is involved. The service life of the application weld beads is limited.
The invention is based on the object of creating a surface armoring suitable for the autogenous wear protection with application of grid armoring technology, particularly for the grinding rollers of high-pressure roller mills or, respectively, roller presses for pressure comminution of granular material, that exhibits a long service life capability as a result of high wear resistance and pressure resistance and that can nonetheless be fabricated relatively simple and cost-beneficially overall and that can also be repaired.
Given the inventive surface armoring of grinding rollers or, respectively, press rollers, depressions spaced from one another are formed in the outside surface of the roller jacket, this being especially easy to accomplish when the roller jacket is composed of a cast metal member, so that any and all chip-removing processing operations such as the application of channels, bores, etc., can be eliminated. Viewed in plan view, the depressions of the roller jacket can be circular, oblong, polygonal, rectangular or rhombic with tips in circumferential roller direction or with tips in axial direction as well. Corresponding, prefabricated, highly wear-resistant hard bodies, particularly of sintered metal, can be fitted into these depressions. The bottom of the depressions and the underside of the hard bodies have been manufactured with a specific surface roughness, for example by hammering, so that cavities can form between the underside of the hard bodies to be fitted in and the bottom of the depressions. Before the hard bodies are fitted into their respective depressions of the roller surface, an adhesive compound is applied in a simple way on the bottom of the depressions and/or on the underside of the hard bodies, this adhesive compound then filling the cavities formed by the surface roughness when the hard bodies are fit in. The hard bodies that have been fitted in are then pressed into their depressions with a tool and a pressure adhesive process is initiated that leads to a very solid connection.
The tool for the implementation of the pressure adhesive process can be an hydraulic of a mechanical press. Especially advantageously, the tool is a hot shrink ring inverted around the hard bodies that have been fitted in, this having been heated to a temperature of, for example, 200xc2x0 C. and being in turn removed after it has cooled, i.e. after shrinking from the hard bodies that have been pressed in, to which end the shrink ring serving as tool is composed of at least two parts, for example two ring halves.
In order for the shrink ring serving as tool to be able to carry out its function of pressing the hard bodies into the depressions of the roller jacket well and the shrink ring lies flush against the upper sides of the hard bodies to be pressed in, it can be advantageous that the shrink ring comprises radially inwardly directed elevations at its inside in those zones that lie opposite the hard bodies to be pressed in, said elevations having the same shape as the hard metal bodies to be pressed in.
According to a further feature of the invention, the adhesive compound for producing the glued connection between the hard bodies and the bottom of the depressions can also be provided with hard metal splinters such as, for example, hard metal carbide splinters, as a result whereof the strength of the glued connection is further enhanced.
The inventive surface armoring is highly wear-resistant and yet comparatively simple to manufacture. If a glued connection of a hard body were to release during operation of the roller press or, respectively, inter-particle roller mill, then the operator himself can repair the roller surface given such damage. The interspace zones of the roller jacket between the hard bodies fitted into the roller jacket depressions can be protected against wear during operation of the roller machine by the initially described, autogenous wear protection.
The invention and further features and advantages thereof are explained in greater detail on the basis of the exemplary embodiments schematically shown in the Figures.